As briefly shown, there is a growing community of researchers that are exploring the possibility of using a CPG to create locomotion in robots [1]}. Most of the previous works in the literature present an open-loop CPG which does not include any sensory information: in [2]}, the actuation of a lamprey-like robot is done by using an open-loop CPG and neuromorphic hardware. Then, in [3]} and [4]}, the authors proposed a CPG implemented on an FPGA and the SpiNNaker platform [5]}; these three works do not offer the possibility of changing the originally produced pattern in real time. However, they showed that implementing CPG using spiking neurons uses less power. There is a more recent paper which allows both real time functioning and pattern variation but without including any sensory information [6]}. In [7]}, the open-loop CPG is implemented on Loihi [8]} using an astrocytic network, producing two different gaits with 24 motor neurons.
However, the most recent work [9]}, proposes the implementation of a CPG with the possibility of changing the amplitude, frequency and phase online without any sensory input required. The authors also pointed out that the architecture should include sensory feedback to modify the behavior of the CPG. That is the objective presented in this paper. We propose an SNN that, using the sensory information, adapts the behavior of the CPG.
Regarding works that include sensory information, in [10]}, the CPG is built using coupled-oscillators instead of spiking neurons and the feedback to the CPG is included into the control loop of the equations of the CPG. In [11]}, 12 simulated neurons modulated by sensory feedback are used to build the CPG. Instead of what we propose, an adaptation SNN, they achieve different gaits by either moving the location or increasing the number of neural structures. The neuron model used is Izhikevich instead of the LIF model proposed in this work to reduce the computational resources used. The sensory information is used to adapt the time duration of each phase of the frequency switching to enable the actuators to reach the commanded position. Finally, in [12]}, a neuromorphic sensor has been used to select which predefined gait of the CPG should be activated. In most of these works, the use of an external input to the CPG changes the performance of it. This performance can be defined as a neuromodulation. It has been shown that this modulation is essential to alter the behavior of a neural structure by modifying the synaptic connections [13]}.
